Key Takeaways & Executive Findings
- •• A novel triphenylamine-based phosphonic acid (1PA-TPD) enables robust covalent anchoring to ITO, overcoming the weak hydrogen bonding of conventional PA-SAMs. • The optimized mixed SAM system (60 wt% 1PA-TPD + 40 wt% EtCz3EPA) effectively suppresses interfacial degradation between PA-SAMs and perovskites. • The molecular engineering strategy simultaneously enhances substrate binding, inhibits interfacial reactions, improves crystallinity, and passivates defects. • This approach paves the way for ultra-stable perovskite solar cells meeting stringent operational standards.
Abstract
Metal halide perovskite solar cells (PSCs) are revolutionizing next-generation photovoltaics by combining high efficiency with low-cost solution processing and flexible compatibility. Certified efficiencies now surpass 27%, nearing the theoretical limit for single-junction cells and highlighting their strong potential for commercialization. In contrast to traditional silicon cells, which require high-temperature processing and rigid substrates, PSCs can be fabricated near room temperature using earth-abundant materials, significantly lowering energy consumption and production costs. However, their commercialization is hindered by a fundamental challenge: insufficient long-term operational stability. PSCs must endure harsh real-world conditions, including elevated temperatures (≥85 °C) and full-spectrum illumination. Meeting the International Electrotechnical Commission (IEC) standard of ≥25 years of service life remains an unresolved critical hurdle for SAM-based PSCs. The hole-transport layer (HTL) plays a decisive role in both the efficiency and long-term stability of PSCs, responsible for efficiently extracting photogenerated holes from the perovskite layer to the transparent conductive oxide electrode. Inadequate extraction leads to severe interfacial charge recombination and significant efficiency losses. Among various HTL materials, phosphonic acid-based self-assembled monolayers (PA-SAMs) have become the material of choice for inverted-structure PSCs, owing to their molecular-scale precision, ultrathin film formation, and superior energy-level alignment—properties that effectively suppress non-radiative recombination and enhance initial device performance. Nevertheless, their practical application is severely limited by an inherent flaw: PA-SAMs primarily anchor to ITO surfaces via weak hydrogen bonds, which dissociate under photothermal stress. This triggers molecular desorption and migration into the perovskite layer, inducing degradation and eventual performance decline. To tackle this persistent issue, Fei et al. report a transformative molecular engineering strategy that unlocks ultra-stable PSCs (Science 2026, https://doi.org/10.1126/science.adz7969). The team designed a triphenylamine-based phosphonic acid (1PA-TPD) with robust covalent anchoring to ITO substrates and optimized a mixed SAM system (60 wt% 1PA-TPD + 40 wt% EtCz3EPA), successfully suppressing interfacial reactivity between PA-SAMs and perovskites. This multifunctional strategy integrates strong substrate binding, interfacial reaction inhibition, crystallinity enhancement, and defect passivation.
1. Introduction
Metal halide perovskite solar cells (PSCs) are revolutionizing next-generation photovoltaics by combining high efficiency with low-cost solution processing and flexible compatibility. Certified efficiencies now surpass 27%, nearing the theoretical limit for single-junction cells and highlighting their strong potential for commercialization. In contrast to traditional silicon cells, which require high-temperature processing and rigid substrates, PSCs can be fabricated near room temperature using earth-abundant materials, significantly lowering energy consumption and production costs.
However, their commercialization is hindered by a fundamental challenge: insufficient long-term operational stability. PSCs must endure harsh real-world conditions, including elevated temperatures (≥85 °C) and full-spectrum illumination. Meeting the International Electrotechnical Commission (IEC) standard of ≥25 years of service life remains an unresolved critical hurdle for SAM-based PSCs. The hole-transport layer (HTL) plays a decisive role in both the efficiency and long-term stability of PSCs, responsible for efficiently extracting photogenerated holes from the perovskite layer to the transparent conductive oxide electrode. Inadequate extraction leads to severe interfacial charge recombination and significant efficiency losses.
Among various HTL materials, phosphonic acid-based self-assembled monolayers (PA-SAMs) have become the material of choice for inverted-structure PSCs, owing to their molecular-scale precision, ultrathin film formation, and superior energy-level alignment—properties that effectively suppress non-radiative recombination and enhance initial device performance. Nevertheless, their practical application is severely limited by an inherent flaw: PA-SAMs primarily anchor to ITO surfaces via weak hydrogen bonds, which dissociate under photothermal stress. This triggers molecular desorption and migration into the perovskite layer, inducing degradation and eventual performance decline.
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LI Xu, GUO Yuxiao, LUO Xin, YAN Haoyuan, XU Bo (2026). Mitigating phosphonic acid-perovskite interfacial degradation via molecular engineering for ultra-stable solar cells. SinoTechIntel Verified Research. https://doi.org/10.1088/1674-4926/26020002
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Frequently Asked Questions
What is the main challenge addressed in this research?
The main challenge is the insufficient long-term operational stability of perovskite solar cells, specifically the interfacial degradation caused by weak hydrogen bonding of phosphonic acid-based self-assembled monolayers (PA-SAMs) to ITO, which leads to molecular desorption and migration into the perovskite layer.
How does the proposed molecular engineering strategy improve stability?
The strategy introduces a triphenylamine-based phosphonic acid (1PA-TPD) that forms robust covalent bonds with ITO, and optimizes a mixed SAM system (60 wt% 1PA-TPD + 40 wt% EtCz3EPA) to suppress interfacial reactivity, enhance crystallinity, and passivate defects, thereby improving device stability.
What are the key components of the new SAM system?
The new SAM system consists of 60 wt% 1PA-TPD (a triphenylamine-based phosphonic acid) and 40 wt% EtCz3EPA, which together provide strong substrate anchoring and effective interfacial protection.
What is the significance of this research for perovskite solar cell commercialization?
By addressing the critical stability issue, this research brings perovskite solar cells closer to meeting the IEC standard of ≥25 years service life, which is essential for commercial viability.
What are the potential applications of this technology?
This technology can be applied in the fabrication of ultra-stable perovskite solar cells for various applications, including building-integrated photovoltaics, portable electronics, and large-scale solar farms, where long-term durability is crucial.
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